The spectacular colours displayed by males during courtship often result from sexual selection by female choice. Female visual perception and preferences for colour should therefore play a critical role in the evolution of male colours. In guppies, female preferences change repeatedly across populations, presenting a great opportunity to study the genetic mechanisms behind changes in female preferences and mate choice. an. In order investigate the genetic mechanisms of female’s preference for colour, I initially studied opsins, the visual pigments that mediate vision, to estimate how much they vary in females with a clear preference for colourful males and females that have lost this preference. Then I moved on to investigating the genetic basis of female mate choice decisions beyond the eye, in the brain’s visual lobes. To do this I used a combination of behavioural experiments and genomics to identify the genetics pathways that get activated in the female brain when evaluating the nuptial colours of a male. Specifically, I started by evaluating the total number of opsin genes, their conservation across populations as well as variation in opsin sequence and expression. Next I relied on next-generation sequencing, to study the neuromolecular pathways underlying guppy mate preference response in the main visual areas of the brain – telencephalon and optic tectum – of females evaluating attractive males compared to non-attractive males. Although I did not find major differences in the opsins, suggesting all females perceive colour similarly, I am beginning to determine which genes and pathways are turned on in a guppy female’s brain when evaluating males. For example, I found 12 genes are differentially expressed in the telencephalon between females exposed to attractive and non-attractive males, and 162 in the optic tectum. Some of these genes are associated with and organism’s response to stimulus, steroid hormone activity, synaptic plasticity and social behaviour.
The results of this work will provide a cohesive, integrative and multi-faceted understanding of the role of opsin variation in this model system of evolution by sexual selection, and will determine the role of opsins and the visual system in driving female mate preferences and male colour evolution. This project will help us understand the genetic underpinnings of key adaptive traits, linking genes to the phenotype and opening up new research agendas. The initial results of this work have been published in Science Advances (in press) and Nature Communications (8:14251 - doi:10.1038/ncomms14251).
